1. Field of the Invention
The present invention relates to an electrode device for a medical apparatus for stimulating living tissue with electrical impulses, of the type having at least two coiled conductors which are electrically and mechanically interconnected in a contact area.
2. Description of the Prior Art
A medical electrode is disclosed in U.S. Pat. No. 4,817,634 which has two coiled conductors which are mechanically and electrically interconnected in a contact area. The document describes a defibrillation electrode comprising an electrode catheter in which a first coiled electrode conductor runs, and an electrode carrier on which a second coiled electrode conductor is arranged in a specific pattern. One end of each electrode conductor is inserted into a coupling sleeve which is crimped onto the ends to electrically and mechanically interconnect the two electrode conductors. The defibrillator electrode is designed for implantation in the heart of a patient.
In an alternative version, of this known device, a plurality of electrode conductors are arranged in simple, closed loops on the electrode carrier. All the conductors are mechanically and electrically coupled in the coupling sleeve.
Coupling conductors with a coupling sleeve have certain disadvantages. In assembly, crimping of the coupling sleeve must be firm enough to prevent detachment of any conductor, which would break the electrical connection. The crimping, however, must not be too forceful, since it might then damage the conductors. When a plurality of conductors is to be interconnected, there is a risk of one of the connections being defective. Since the aforementioned known electrode device is to stimulate the heart, it is exposed to constant, dynamic loading. The contact area is therefore subjected to a large number of load changes which could cause conductor fatigue in the attachment area, since the coupling sleeve is completely inflexible but the conductors are flexible. The conductors are also connected in a contact sleeve which restricts the design of the specific pattern in which the conductors are arranged. If more than one contact sleeve were used when a plurality of conductors is arranged on the electrode carrier, the entire defibrillation electrode would be stiff and obstruct the heart's movements. Moreover, coupling cannot be disengaged, and the number of parts required for assembly of the electrode device increases.